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Has anyone constructed a DIY motorized dolly?


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#1 Buddy Greenfield

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Posted 24 December 2007 - 02:31 AM

I know there is no substitute for the real thing and that in most cases the easiest, safest and often least expense route is to just buy or rent the right gear for a given job, but that said, I enjoy examining how stuff works and building things, so if possible I?d like any ideas on what kind of (Perhaps common) motors, drive train etc. I might use to propel a riding dolly.

I'm only doing MOS right now, so motor noise isn't a factor.

-Thanks-
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#2 Onno Perdijk

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Posted 27 December 2007 - 05:26 PM

Hello Buddy,

When going for a DIY motorized dolly you need a lot of time at first! There are so many options, all depending on speed, payload, accelaration, deceleration, exactness in speed and position, available current....
I have been working on nearly all options available, from powerdrill-driven-ropes and pulley's up till motioncontrol units and only for the lower-payloads (uptill 75kg) and I do not want to disencourage you but for the options in between powerdrill and Moco it will be hard to find a way to control the motorunit.

For a DIY in a low-payload-configuration you could start with an electrical step/scooter with air tires. Remove the airtire and use this as a pulley with a rope with no stretch, with a pulley at the other side of your track. This will give you a speed of 2meter per second with a 50kg payload on a flatbed dolly....

Good luck!

Onno Perdijk
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www.solidgripsystems.eu
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#3 Buddy Greenfield

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Posted 27 December 2007 - 09:01 PM

Onno,

Thanks for the repsonse. Good to know I'm not the only person here crazy enough to try it.

It seems some sorta of centrifugal clutch assembly might be in order to help alleviate the jolt of direct drive. I've been wondering about how much torque I might get from a sewing machine assembly, but I can see what you mean by many factors having to be overcome, I imagine vibration would be an issue as well.

I've seen a few variations upon the cordless drill approach, but I need payload power like from perhaps one of those "Scooters" the elderly use.

I hope Grandma knows how to frame a nice shot, or she's fired! :lol:

Thanks
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#4 Jaron Berman

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Posted 27 December 2007 - 09:58 PM

How about a dolly grip?

Not sure exactly what effect you're going for, but usually the simplest solution is the best one. No small motor will be able to start and stop a dolly w/ AC and Op as fast or gently as a grip will. If it's for motion control, the pulley and cable probably won't be accurate enough to make repeatable moves, you'll probably need to put the camera on a remote head to drop the lbs, and come up with a direct drive to the track that is repeatable - some kind of close loop servo system that knows where it is at all times.


If its an experiment, you could always try it out on a smaller scale...perhaps something large enough for a camera but not a rider. Some lightweight track spread between tripods or even leveled saw horses could hold a camera on a small, motorized dolly. The less mass you have to move, the less force you need to move it. With less moving mass, you can either down-size your motors, or work out your gearing so they can start and slow the dolly more quickly and accurately. Check out the P&S technic Skater Dolly:

http://www.pstechnik.de/en/skater.php

with a DIY version, you wouldn't have to use Heden or Preston servomotors - you could definitely substitute cheap gear-head motors or steppers (if you know how to control them).

Or, again, you could just have someone push the dolly.
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#5 Buddy Greenfield

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Posted 28 December 2007 - 01:27 AM

Jeron,

Thanks for the info. The Skater stuff looks great, but also out of my budget realm.

After film stock I don't have any money, just tools,creativity and lots of black spray paint.

As embarassing as it is to admit, I actually make most of my stuff from things people throw away. My dolly is made from a table, office chair, garage door rollers and conduit. lol
It works pretty good and the price was right. I made some cool easy to do snoots that get the job done for nothing as well, but it IS starting to look like I'm shooting a Sanford and Son remake.

Thanks

Edited by Buddy Greenfield, 28 December 2007 - 01:31 AM.

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#6 Jaron Berman

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Posted 29 December 2007 - 10:48 PM

Homemade stuff works in a pinch. Not sure if you've seen it but this is a great resource for all sorts of things grip related:

http://www.rondexter.com

As for the skater - just using it as an example of a small motorized camera dolly. No reason you couldn't improvise something similar should you need to.
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#7 Buddy Greenfield

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Posted 29 December 2007 - 11:30 PM

Awesome link!

Ahhh, sorry I didn't get that you intended the Skater stuff as an example, good call.
I agree, in a pinch you do what you can. (Then you spray paint it black and hope it's in focus. lol )

"Improvise" is a key word. It seems everytime I see "Making Of" footage, no matter the budget, or what they can buy or rent on a whim, there is always something improvised to get the job done.

Thanks
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#8 Jaron Berman

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Posted 03 January 2008 - 08:49 PM

Absolutely. Good grips are worth their weight in gold. For some, that's a lotta gold!

Seriously, though, I've seen grips work like magicians and save my (and production's) arse. Not every production has the luxury of skilled producers, and the extravagance at the beginning can end up as shoestrings in the end. When it comes down to getting the shot or not, having the experience of improvising can really be helpful. Knowing how much you can get away with is certainly as important as knowing how the cadillac equipment functions.
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#9 John Sprung

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Posted 04 January 2008 - 01:28 PM

I'm only doing MOS right now, so motor noise isn't a factor.

But it should be fairly easy to make it quiet, which will be an advantage well worth having.

For the very latest and greatest in DIY motor control, look around for the environmentalist types who build their own electric cars. You have basically the same qualitative requirements, but with much lower speed, payload and distance requirements. I remember seeing a place called Green Motor Works here in LA.

Another place to look is the traditional golf cart/warehouse cart business. Taylor-Dunn is the big name:

http://www.taylor-dunn.com/index.aspx





-- J.S.
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